This invention claims priority of the Swiss patent application 2000 1898/00 filed Sep. 28, 2000 which is incorporated by reference herein.
The invention concerns a stand having a balancing device.
Stands, in particular for surgical microscopy or the like, should be properly balanced so that the microscope can be pivoted, lifted, lowered, and moved in space with relatively little application of force. The existing art discloses several methods for balancing, including semi-automatic or automatic balancing methods, in which a balance status is measured via a force or displacement sensor and an electrically controlled balancing action is performed on the basis of that measurement.
The term xe2x80x9celectrically controlled balancing actionxe2x80x9d is to be understood, for example, as the activation of an electric drive that displaces balancing weights. One example of such a balancing device has been disclosed in the applicant""s PCT international patent application WO-A-97/13997.
The conventional and hitherto published balancing systems with electrical or electronic assistance are based on the assumption that the imbalance is measured as a physical magnitude, and the balancing operation is performed on the basis of the measurement result. This requires corresponding force measurement sensors and a corresponding measurement operation; only after that can the balancing operation take place. Because they are located on moving systems, such force measurement sensors and the electronic amplifiers necessary for them are usually complex and expensive. Leaving this aside, the balancing operation is always reactive, since first measurement occurs and then balancing. With some stands of the existing art with semi-automatic balancing, for example, after an accessory change a button on the stand that initiates the balancing operation must be pressed.
With such systems, a certain time therefore also elapses before the balanced state is achieved.
The fully automatic balancing systems described in the literature have, compared with the button-controlled systems, the (sometimes undesirable) characteristic that they balance out a stand even when the balancing operation is not desired. For example, when the stand is balanced and a surgeon then leans against or holds onto the microscope, in fully automatic systems this can immediately result in a balancing operation. When the bracing forces on the microscope are released, e.g. when the hands are released or the head pulled back, this balance operation can result in a severe imbalance. This must first be detected and compensated for by another balancing operation. During this period the microscope is not fully usable by the surgeon, thus in some circumstances preventing him or her, during this detection and balancing operation, from continuing the surgical procedure until this new balancing operation is complete. In the case of an automatically operating stand of the applicant (OHS), this balancing is therefore performed not continuously but only after switching into balancing mode. But if an assistant adjusts or replaces accessory parts during the procedure, the microscope is then at first no longer balanced. To allow the surgeon to work unhindered, another time-consuming balancing action (switching over into balancing mode) is necessary, and the surgery must be interrupted during this period.
The Mxc3x6ller-Wedel company has proceeded from another consideration in its stand design. First a mechanical balance is achieved. If components on the microscope are then replaced, this balance is not disturbed at all but rather adjustments intended to re-establish balance are performed on the components themselves, or on other components present on the microscope. For example, the assistant""s tube is pivoted so that a balanced state is achieved.
This is often unsatisfactory, however, since a position that does not conform to the desired working position is thereby established.
It is the object of the invention to find a new balancing system which dispenses with complex and expensive force or displacement sensors and performs a balancing operation, avoiding any interruption of the surgical procedure, as immediately and quickly as possible as soon as any modification to the accessories of the microscope occurs, without previously performing a measurement operation of physical magnitudes such as forces, deformations, or the like; and in which an undesired balancing operation resulting from bracing forces, as described above, is prevented.
The particular aspect of the present invention is a completely new philosophy: there is no intention to measure physical forces or displacements (deformations) that provide some information about the balance state; instead a complete computer-assisted mathematical model of the stand is provided. The addition or removal of components to or from this model (addition or removal of accessories to or from the microscope or change in the position of essential components) causes the computational model to be correspondingly modified; the corresponding change in the model is taken into account computationally, and on the basis of the computational model the control commands for the electrical activation of counterweights are initiated.
As compared to the existing more or less intelligent balancing systems (imbalance is measured by means of intelligence and balanced out by means of an intelligent control system), for the first time according to the present invention an intelligent stand is put into service. The intelligent use of a computer and corresponding programming or calibration means that the stand xe2x80x9cknowsxe2x80x9d its configuration and recognizes any change to its configuration, in order to carry out corresponding balancing actions by means of direct activation of counterweights or the like.
What is provided first of all according to the present invention is therefore a computer that contains a program with which the balance states can be calculated and the absence of balance is ascertained computationally, by the fact that the added or removed components (e.g. accessory parts on the microscope) are entered along with their properties that influence the overall model. This input is preferably accomplished in coded form, so that information about the accessory part added to or removed from the microscope can be entered into the computer, for example manually or by means of a barcode reader or the like.
For example, each accessory part bears a number that the user communicates to the computer via a keypad before installing the component. In accordance with a particular embodiment of the invention, automatic recognition of the accessory parts is provided for in order to speed up this operation. This is accomplished, for example, by way of an automatically readable barcode that is applied to a location on the accessory part that is automatically sensed by a reading device upon installation.
According to a further particular embodiment of the invention, a microchip having the corresponding information written into it (for example, a microchip like that on a check card) is provided instead of a barcode.
Of course magnetic or other data media or the like could also take care of the corresponding information transfer between accessory part and computer. What is favorable with this configuration is that the computer automatically and immediately detects, without further intervention, which accessory parts have been removed from the microscope and which have been added. Since all these components are included in the computational model, the correct balance position of the counterweights can be set directly and immediately.
Balancing thus takes place substantially more quickly than with conventional stands. The intelligence for the actual balancing operation can in fact be reduced (and can thus be cheaper) as compared to the known semi-automatic or automatic balancing systems.
With a configuration according to the present invention, once a balancing operation has been performed it is also not influenced by pressure from the operator""s head or hands. Such operations are not even encompassed by the computer or the mathematical model.
A further particular embodiment of the invention provides for the provision, in addition or alternatively to the information-transferring part (chip, barcode, or the like), of angle sensors or displacement sensors which sense the positions of pivotable parts of the accessories and, on the basis of a specific pivot position of said parts, signal to the computer (optionally via the chip) and to the computational model of the balancing system a change that makes possible or triggers a balance correction. In contrast to the force measurement sensor systems used hitherto in balancing systems, angle sensors are very inexpensive; in addition, the demands made on them are not particularly great, since slight changes in the angular position of, for example, a tube do not have a substantial effect on the imbalance of a fully balanced stand.
As part of a development of this inventive embodiment, there is provided for the angle sensor and for the chip connected to it a suitable logic system that continuously supplies the corresponding balance information to the computer. In this case it is not absolutely necessary for the accessory part information to be coded and stored in tabular form in the computer; instead the mathematical model is calculated automatically in each case on the basis of the balance information read in automatically by the respective accessories.
The specific configuration of the stand is not critical for implementation of the actions according to the present invention described above. The assemblage can have parallelogram supports or standard beam supports or the like. Conventional stands can easily be retrofitted with what is proposed according to the present invention, since as a rule only additional data lines and data acquisition elements need to be installed.
As an alternative to data lines and electronically connected systems, accessory parts that can be connected to the computer by means of infrared sensors or other telecommunication devices (for example ultrasound or radio waves) are also conceivable. For example infrared light-emitting diodes or reflectors, for example such as those described in the applicant""s European Patent Application EP-A-822 436, can be constructed. In other words, light pulses proceeding from the accessory part communicate their balance characteristics information to the computer via corresponding light pulse receivers.
The invention also makes it possible to develop a standard for accessory parts that permits the universal utilization of accessory parts on different systems having a balance computer according to the present invention. The invention also allows a customer""s own accessory parts to be calibrated at the manufacturer""s facility by providing there a reference stand on which, by means of conventional balancing system measurement devices, the balance characteristic of the corresponding accessory part is determined and is then coded thereon. This can be accomplished, for example, by way of the barcode, a chip, or another code that is optionally supplied additionally by means of a computer diskette.
Of course the invention is not limited to a pure balancing apparatus corresponding to the above inventive features; on the contrary it also allows for a combination with conventional automatic or semi-automatic balancing systems if advantages for the user may be derived therefrom. What is critical in any event is that by way of the balancing system according to the present invention, optimum and immediate balancing can be effected directly without further measurement operations.
The present invention is also particularly suitable for balancing directly at the optics support, i.e. for pivoting movements of the microscope about a horizontal axis and at least one farther axis that is arranged at an angle to the horizontal axis. For balancing according to the present invention in the context of a pivot support (a pivot support is that component which directly holds the microscope and which gives the microscope mobility in space by way of at least one, as a rule two to three, pivot axes, and which in turn is mounted on supporting elements of the stand) according to the present invention balancing is performed in such a way that by way of the electrical drives, the center-of-gravity axes and the intersection of the pivot axes of the stand are displaced relative to one another in such a way that the intersection of at least two pivot axes (or even three or more pivot axes) ends up at the center of gravity of the microscope or of the microscope having the assemblage joined directly to the microscope.
This balancing action can be brought about by the displacement of counterweights that displace the center of gravity of the microscope or of the assemblage; or by the displacement of pivot axes so that their intersection ends up at the center of gravity; or by displacement of the microscope or the relevant accessory parts relative to the corresponding pivot axes of the microscope, so that its center of gravity is placed on the intersection of the axes.
Optimal balancing of the pivot support exists when the intersection of all the pivot axes is located exactly at the center of gravity of the movable assemblage (microscope with accessories).
In an embodiment, the invention provides in particular for balancing to occur according to the present invention on a stand both in the pivot support and on the other supports.